System for controlling engine using variable valve lift and method thereof

Abstract

A system for controlling an engine includes a driving information detector detecting driving information. At least one intake valve and at least one exhaust valve open and close the combustion chamber. A variable valve lift (VVL) system adjusts opening timing of the intake valve and the exhaust valve. A compressor rotates by a rotational force of a turbine and compresses intake air, and a vane adjusts the amount of exhaust gas supplied to the turbine. A controller controls opening of the vane using a high pressure EGR valve, when the exhaust valve is open during a suction stroke by the VVL system, the vehicle accelerates or decelerates, and an air/fuel ratio is beyond reference ratio range.

What is claimed is: 
     
       1. A system for controlling an engine comprising:
 a plurality of sensors configured to detect driving information including a vehicle speed, an engine speed, a fuel injection amount, an atmospheric pressure, an intake air temperature, and a displacement of an accelerator pedal; 
 at least one intake valve and at least one exhaust valve opening and closing a combustion chamber; 
 a variable valve lift (VVL) system, implemented by a first processor, configured to adjust opening timing of the at least one intake valve and the at least one exhaust valve; 
 a turbocharger including: a turbine which rotates by exhaust gas exhausted from the combustion chamber; a compressor which rotates by a rotational force of the turbine and compresses intake air; and a vane which adjusts an amount of exhaust gas supplied to the turbine; and 
 a controller, implemented by a second processor, configured to determine whether the exhaust valve is opened during a suction stroke by the VVL system, whether a vehicle is accelerated or decelerated, and whether an air/fuel ratio is within a reference ratio range, and control opening of the vane according to a target exhaust gas recirculation (EGR) rate and an amount of air flowing into the combustion chamber using a high pressure EGR valve when it is determined that the exhaust valve is open during the suction stroke by the VVL system, the vehicle accelerates or decelerates and the air/fuel ratio is not within the reference ratio range, 
 wherein the combustion chamber provides a driving torque by combustion of a fuel. 
 
     
     
       2. The system of  claim 1 ,
 wherein the target EGR rate is determined according to a pressure difference between an intake manifold and an exhaust manifold of the engine and a pressure of the intake manifold. 
 
     
     
       3. The system of  claim 2 ,
 wherein the target EGR rate decreases as the pressure difference decreases, and the target EGR rate increases as the pressure difference increases, and 
 the target EGR rate decreases as the pressure of the intake manifold increases, and the target EGR rate increases as the pressure of the intake manifold decreases when the differential pressure is maintained to be the same. 
 
     
     
       4. The system of  claim 1 ,
 wherein the controller determines whether the vehicle accelerates or decelerates based on a vehicle speed variation, an engine speed variation, or the displacement of the accelerator pedal. 
 
     
     
       5. The system of  claim 1 ,
 wherein the controller controls the opening of the vane according to the target EGR rate and the amount of air flowing into the combustion chamber using the high pressure EGR valve only when it is determined that the air/fuel ratio is not within the reference ratio range. 
 
     
     
       6. The system of  claim 1 ,
 wherein the controller sets a target boost pressure and a target amount of air flowing into the combustion chamber from the detected driving information and feedback-controls a boost pressure and the amount of air according to the target boost pressure and the target amount of air when it is determined that the exhaust valve of the combustion chamber is not opened during the suction stroke, the vehicle does not accelerate or decelerate, or the air/fuel ratio is within the reference ratio range. 
 
     
     
       7. The system of  claim 6 ,
 wherein the controller controls the opening of the vane of the turbocharger by comparing the target boost pressure to an actual boost pressure and the high pressure EGR valve by comparing the target amount of air to an actual amount of air.